Tire Size Calculator
Estimates tire sidewall height, overall diameter and circumference from the tire size markings.
How it works
Tire dimensions
Formula and assumptions
Sidewall height in mm = width × aspect ratio ÷ 100. Overall diameter in inches = 2 × sidewall height ÷ 25.4 + rim diameter. Actual dimensions vary by tire manufacturer and model.
Example
Use the sample values, calculate, and change one input at a time.
Frequently asked questions
Are results exact? Results depend on the assumptions and inputs above.
Can I use this for professional decisions? Verify critical results independently.
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Frequently asked questions
Is the result the exact tire diameter?
It is a nominal estimate from the marked tire size; actual dimensions vary by make and model.
What should I check before relying on the result?
Confirm the input units and assumptions described above; independently verify safety-critical, medical, financial or professional decisions.